/Engine/Source/Runtime/Engine/Classes/Camera/PlayerCameraManager.h
Implementable blueprint hook to allow a PlayerCameraManager subclass to constrain or otherwise modify the camera during free-camera photography. For example, a blueprint may wish to limit the distance from the camera's original point, or forbid the camera from passing through walls. NewCameraLocation contains the proposed new camera location. PreviousCameraLocation contains the camera location in the previous frame. OriginalCameraLocation contains the camera location before the game was put into photography mode. Return ResultCameraLocation as modified according to your constraints.
void PhotographyCameraModify ( const FVector NewCameraLocation, const FVector PreviousCameraLocation, const FVector OriginalCameraLocation, FVector & ResultCameraLocation )